Aberrant Extracranial Branch Prevents Internal Carotid Artery Occlusion

The internal carotid artery (ICA) is a terminal vessel that does not give rise to branches in the extracranial segment. The ICA occlusion typically extends to the first intracranial branch, the ophthalmic artery. We present a rare case of isolated ICA occlusion with distal patency due to an aberrant extracranial branch. A 52-year-old man with longstanding tobacco use, hypertension, hyperlipidemia, diabetes, and extensive coronary artery disease was referred to the vascular laboratory for evaluation of carotid disease. The patient had no history of transient ischemic attack (TIA), amaurosis fugax, or cerebrovascular accident. Carotid duplex results prompted further evaluation by computed tomography angiography (CTA). Duplex imaging demonstrated right common carotid artery (CCA) plaque with significantly elevated velocities and turbulent flow extending into the ICA. Mild heterogeneous plaque was noted proximally in the left ICA followed by less than 2-cm occlusion and reconstitution of flow in the distal extracranial segment. The CTA testing revealed a moderate right CCA stenosis, mild proximal left ICA plaque and an isolated occlusion of the mid-ICA and distal reconstitution via an aberrant collateral branch. The left intracranial ICA segment remained patent throughout its course but was of smaller caliber. Aberrant branches of the extracranial ICA are unusual and rarely identified by carotid duplex analysis. Awareness of this anomaly underscores the importance of determining patency of distal ICA flow in the presence of an occluded proximal segment; aberrant collaterals can make surgical exploration and endarterectomy in these patients feasible